This invention relates to a system for sensing remote events and for transmitting and boosting a digital data signal representing the sensed events on a transmission line.
In the field of telemetry, there are a number of systems which employ a variety of sensors for sensing physical events (e.g., sound, light, movement, temperature, stress, etc.) and for transmitting sensor signals over electronic transmission lines to a central receiving station. One example of such a telemetry system is a towed sonar array system which comprises a plurality of hydrophones connected to a transmission line (e.g., a coaxial cable) which is in turn connected to a central data receiving station. The towed array is placed in water and is towed by a vessel (e.g., a submarine) for detection purposes. Each of the sensors is capable of generating an analog sensing signal which is converted into a digital data signal by an A/D converter. The digital data signal is injected onto the transmission line for transmission to the central data receiving station.
Due to the limited data transmission capacity of metallic transmission cables, there has been a need in the art for circuitry which is capable of compensating for the propagation losses of the digital data signal transmitted on the transmission lines. Such circuits have, in general, consisted of repeater circuits and/or resynchronizers which are placed at predetermined intervals along the transmission line in order to amplify the signal. However, because of the serial nature of these repeater circuits, sensor array systems employing these repeater systems are unreliable. That is, if one repeater in the array fails, data transmission is seriously attenuated or ceases altogether. In addition, the prior art repeater systems are relatively heavy, making them less desirable for use in the seawater environment of the towed sonar array. Thus, there is a need in the art for a telemetry system including a circuit for boosting a digital data signal, which is both light in weight and which does not have a seriality problem, so that if one of the booster circuits fails, the remaining booster circuits are capable of amplifying the digital data signals to compensate for any propagation losses.